Rotary flow separator for fine grain particles

ABSTRACT

A rotary flow separator for sifting fine grain particles in which the particle inlet comprises a narrow annular gap and which has a single ring of secondary air nozzles arranged so that the distance from the particle inlet to the secondary air nozzles may be adjusted.

i United States Patent 11 1 Klein et al.

[ Nov. 4, 1975 ROTARY FLOW SEPARATOR FOR FINE GRAIN PARTICLES Inventors: Heinrich Klein; Rudolf Pieper, both of Erlangen, Germany Siemens Aktiengesellschaft, Munich, Germany Apr. 24, 1973 (Under Rule 47) Appl. No.: 353,949

Assignee:

Filed:

Foreign Application Priority Data Apr. 26, 1972 Germany 2220535 US. Cl. 209/144; 55/261; 55/266;

55/342 Int. Cl. B04C 3/06 Field of Search 209/144, 211; 55/261, 266, 55/456, 457, 447, 468, 342; 210/512 Primary Examiner-Frank W. Lutter Assistant ExaminerRalph J. Hill Attorney, Agent, or Firm-Kenyon & Kenyon Reilly Carr & Chapin [57] ABSTRACT A rotary flow separator for sifting fine grain particles in which the particle inlet comprises a narrow annular gap and which has a single ring of secondary air n02- zles arranged so that the distance from the particle inlet to the secondary air nozzles may be adjusted.

12 Claims, 10 Drawing Figures US. Patent Nov. 4, 1975 Sheet 1 of 4 3,917,568

US. Patent Nov. 4, 1975 Sheet 3 of4 3,917,568

FigAb This invention relates to particle separators in general and more particularly to a rotary-flow separator for sifting fine grain particles.

Various types of rotary flow separators have been 1 used in the prior art for separating and for sifting fine grain particles. In general, such separators comprise a cylindrical, centrifugal chamber with an axial particle inlet at one end and an axial outletfor the gas from which the particles have been separated along with particles which have not been separated at the other end. Within the centrifugal chamber along its cylindrical surface there are arranged a plurality of tangential inlets through which secondary air may be supplied. These are arranged so as to direct the air force through them at an angle to the inlet. To remove the particles which are separated out in the centrifugal chamber, an annular gap which surrounds the particle inlet and opens into a collection bin is provided. Because the raw gas containing the particles to be separated and the secondary air are directed in opposite directions, there is developed within the cylindrical chamber a rotary flow which comprises an inner, axial, helical rotary flow and an outer, also helically, circulating flow in the region near the wall. The inner and outer flows will have components which are in opposite axial directions. At the particle inlets there are provided guide vanes which will set into rotation the raw gas and particles being supplied through the separator. This causes the particles to be thrown out from the inner rotary flow and into the outer circulating flow. The particles are then carried out of the separator by this outer circulating flow through the annular gap surrounding the particle outlet and fall into a bin or a suitable conveyor arrangement. Rotary flow separators of this nature have a very high separation efficiency even for very fine particles. For a given design, all particles over a particular size will be separated out. However, in the process, quite a few particles of smaller size will also be separated out. In dealing with separation, this type of operation is no problem. However, when a sifting action is desired, this type operation is not acceptable. That is to say, in separation the object is that no particles over a given size be allowed to remain in the gas from which the particles are to be separated. What happens to particles smaller than the set limit is not particularly important. On the other hand, in sifting an action like that of the sieve is desired. That is to say, that all particles over the predetermined size should be removed but all particles below that pre-determined size should remain in the gas. There have been attempts to use the type of separator described above as a sifter. In attempting to obtain the sharp cutofi' desired, the secondary air inlet pressure and/or the input rotation through the guide vanes in the particle inlet have been reduced in order to cause the degree of separation to become poorer. The results have been only a very inaccurate approximation of the idea] which was being attempted. Thus, operation with reduced output only will not lead to the desired sharp cutoff characteristics. It can be seen, that there is a need then, for a rotary flow separator which will act to sift fine grain particles.

SUMMARY OF THE INVENTION The present invention provides such a rotary flow separator which permits more nearly approaching the sharp cutoff required in sifting operations. In addition the distance between the particle inlet and the secondary air nozzles is made adjustable so that the cutoff point may easily be adjusted.

In the preferred embodiment, the particle inlet is designed as a narrow annular gap so that the same initial geometrical conditions are imparted to all particles which enter the centrifugal chamber, i.e., the same rotary motion is imparted to practically all particles. In addition the secondary air nozzles are arranged in a single ring. This causes the particles which have been thrown out of the inner rotary flow to be carried by the outer flow to the particle outlet only from a pre-determined height which is accurately defined in the centrifugal chamber. Through this arrangement, a sharper separation of the particles by grain size is possible than with a rotary flow separator operated with reducedoutput.

To obtain the narrow annular gap at the particle inlet, an streamlined body of rotational symmetry, whose cross sectional area is at least half the cross sectional of the particle inlet pipe, is arranged axially within the particle inlet opening. In addition to aid in the adjustment of the distance between the inlet pipe and the secondary air nozzle, the inlet pipe is made to be axially adjustable. In one embodiment, the secondary air nozzle comprises a ring of guide vanes placed between the surface of the centrifugal chamber and the gas outlet pipe. The vanes are attached to the outlet pipe and the outlet pipe with the attached ring of guide vane is made axially movable. In this manner the distance between the inlet and the secondary air nozzles may be adjusted by movement of the outlet pipe as well as through movement of the particle inlet pipe. In addition, an embodiment in which a plurality of sifter units are connected in series, each having different distances between the particle inlet and the secondary air nozzle, and which can thereby sift the particles into separate fractions is also shown. Also shown, is an embodiment wherein the inlet pipe is closed ofi at the lower end of the streamlined body and the gas from which the particles to be separated is fed in through at least one tangential feed line which opens into the ring gap between the streamlined body and the inlet pipe. In addition, the streamlined body may be arranged so that it is replacable and also so that bodies of various diameter may be used to provide different entrance conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a series of curves illustrating different types of separator operations.

FIG. 2a is a cross sectional view of the particle separator of the present invention with an adjustable inlet pipe.

FIG. 2b is the plan view partially in cross section of the embodiment of FIG. 2a.

FIG. 3 is a cross section of a second embodiment of the present invention in which the secondary air ring and outlet pipe are also adjustable.

FIGS. 4A and B illustrate how a tangential inlet pipe may be used and how replacable streamlined bodies of different sizes may be installed in the inlet pipe.

FIG. 5 illustrates in cross section a series arrangement of a plurality of rotary flow sifters.

3 FIGS. 6A through C illustrate the separation obtained in the stages of series arrangement of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates the type of operation possible with various types of separators or sifters. The curve indicated by I illustrates the operation of the conventional particle separator adjusted to separate out all particles above micrometer size. As is evident, although this separator works very efficiently for removing all particles above 5 micrometer, it also removes quite a few particles of smaller size. As noted above this type of operation is permissible only where separation is desired. The type of operation required when sifting is shown by the curve designated II. In the example shown, a sharp cutoff at IO micrometers is desired. That is, no particles below the micrometer size should be sifted out but all particles above the 10 micrometer size should be sifted out. The curve indicated by the dotted line of III shows the type of operation which is obtained with reduced output in a conventional separator such as that described above. The curve of IV illustrates the type of operation obtainable with the present invention. As an examination of the figure will show the type of operation obtainable with the present invention more nearly approaches that of the ideal curve of II.

The basic elements of the rotary flow separator of the present invention are illustrated in FIGS. 2a and 2b. The separator comprises a cylindrical centrifugal chamber 1, having an inlet pipe 2 of smaller diameter inserted from below. The inlet pipe 2 contains an aerodynamic body 4 to form an annular outlet opening 3. The diameter of the streamlined body 4 is such as to only leave a narrow annular gap. In all cases the cross sectional area of the streamlined body 4 should be at least half that of the cross section of the inlet pipe 2. Within the gap 5 are arranged a plurality of guide vanes 6 which will impart rotary motion to the gas and particles which are fed into the separator via the inlet pipe 2. The type of flow which is imparted is illustrated by the heilcal arrow 7. This type of flow results in a centrifugal force upon the particles in the gas or air causing them to be thrown outwardly toward the inside wall of the cylinder 1. The heavier particles will be immediately thrown out toward the wall of cylinder 1 with lighter particles to be thrown out as the flow proceeds upward. Although it is preferable to have the guide vanes 6 to impart this rotary motion, it is possible to achieve sufficient excitation of rotary motion through a flow branch of the outer circulating flow 1 1 to be described below.

At a pre-determined distance x above the inlet opening 3 there is arranged a ring of secondary air nozzles 8. Air under pressure is provided through a feed line 9 into a chamber 10 and thence through the nozzles 8 into the centrifugal chamber 1. As is more clearly shown in FIG. 2B, the flow of air so directed will be tangential to the inner surface of cylinder 1 and in a direction which is downward toward the inlet opening 3. This flow is illustrated by the heilcal circulating arrow 11. This air flow will pick up the particles which have been thrown out by the center rotating flow and carry them to an outlet opening 13 which comprises an annular gap made by placing a diaphragm 12 around the inlet pipe 2. After passing through the gap 13 the particles will fall down into a bin 14 from which they can be removed via an outlet pipe 15. The result is that only the particles which have been thrown out of the inner air flow from the nozzles 8 will be carried into the bin 14 by this air flow. The smaller particles upon which there has not been sufficient centrifugal force to cause them to be thrown outward prior to reaching the nozzles 8 will be carried along with the inner air flow out through an outlet pipe 16.

Because the particles are fed into the chamber through a narrow annular gap 5, they will each have approximately the same rotary motion. Because of the different masses, different centrifugal forces will act on the particles which have been fed in resulting in different trajectories on which they are thrown out of the inner flow 7. As a result the larger particles indicated by the number 17 will be thrown out very soon after entering the centrifugal chambers while the smaller particles indicated by the number 18 reach outward only further up in the centrifugal chamber. From a knowledge of the geometry of the separator and the flow data, it is possible to determine exactly at what height in the centrifugal chamber 1 above the inlet opening 3 particles of a given size will reach the area of the outer flow 11. Only the particles which have reached the outer circulating flow 1 1 below the nozzle ring 8 will be separated out. This allows adjusting the distance x between the inlet opening 3 and the nozzle ring 8 to accurately adjust the grain size above which all particles are separated out. In other words, grain size limit can accurately be fixed within rather narrow bounds by adjusting the distance x. In the embodiment of FIG. 2 such adjustment is carried out by axially moving the inlet pipe 2 within a mounting 17 in the lower end of the chamber 1.

A second embodiment of the invention in which both the inlet pipe 2 and the single row of nozzles are both movable to adjust the distance x is shown in FIG. 3. In this embodiment, the nozzle ring is comprised of a plurality of guide vanes 20 which are rigidly connected to the outlet pipe 21 and connect to the centrifugal chamber 1 with only a flexible sealing means such as a rubber or plastic portion on the end of each vane. The outlet pipe 21 is supported within a support 22 in the top of the chamber 1 for axial motion therein. Thus, the outlet pipe 21 along with guide vanes 20 may be moved up and down in order to adjust the distance x. The secondary air is fed in through an inlet pipe 23 and flows into a chamber formed between the outlet pipe 21 and the walls of chamber 1 and thence through the guide vanes and into the main portion of the cylindrical chamber 1. As shown, the inlet pipe 2 may also be made axially movable to further increase the amount of adjustment possible.

FIGS. 4A and B illustrate an alternate embodiment at the particle inlet. In this embodiment, the inlet pipe 31 in which the streamlined body 30 is inserted is closed off at the bottom with the body 30 resting against the bottom of the inlet pipe 31. The air or gas containing the particles to be separated is fed in through one or two tangential inlet pipes 32 and 33 near the bottom of the inlet pipe 31. This permits eliminating the vanes within the gap between the inlet pipe 31 and streamlined body 30 since the required rotational motion will be imparted to the incoming gas and particles because of the tangential flow at the inlet. This type of construction is advantageous in particular where materials which easily coagulate or are sticky are to be separated. This embodiment offers the further advantage in that streamlined bodies of various cross sectional areas may be placed within the inlet pipe 31 to provide different annular gaps 34 between the body and the pipe 31. An example of different size bodies are shown by dotted lines indicating an aerodynamic body 30 smaller than aerodynamic body 30 and a body 30" larger than the body 30. Throughthe use of different size bodies, rotary motion of different intensities may be imparted to the particles.

An arrangement of a plurality of rotary flow sifters in serial is shown on FIG. 5. As shown thereon there are three separate sifters such as those described above designated as 40', 40 and 40". The distances x, x and x within the three respective separators are different. The separation curve for each separator is shown next to it. The curves are designated FIGS. 6A, 6B and 6C. As shown separator 40 is adjusted to separate all particles above 15 micrometers, separator 40" all particles above 10 micrometers and separator 40" all particles above micrometers. The gas containing the particles to be separated out is provided into the inlet pipe 3 of separator 40 out of which, via the outlet 15 will be separated all particles greater than 15 micrometers. Remaining particles will be provided out of the separator 40' into the separator 40 through the inlet pipe 3". Herein, all particles micrometers and greater will be carried off through the outlet Particles smaller than 10 micrometers will be carried through the inlet pipe 3 into the separator where all particles above 5 micrometers will be forced out. The gas will then exit the separator 40" via the outlet pipe 16" containing particles of zero to five micrometers.

Thus an improved rotary flow separator which is capable of sifting fine grain particles has been shown. Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from the spirit of the invention which is intended to be limited solely by the appended claims.

What is claimed is:

1. A rotary flow particle separator, comprising:

a cylindrical centrifugal chamber;

a coaxial inlet pipe disposed at one end of said chamber;

a coaxial outlet pipe disposed at the other end of said chamber;

a plurality of secondary air nozzles disposed in a single ring arrangement for directing a flow of air tangentially with respect to the inner surface of said chamber and at an angle towards said inlet pipe, the distance between said inlet pipe and said secondary nozzles being adjustable;

a particle outlet disposed concentrically about said inlet pipe and including means for rotating particle laden gas introduced therethrough; and

means for forming an annular gap at the outlet of said inlet pipe.

2. The apparatus recited in claim 1, wherein said inlet pipe is axially adjustable.

3. The apparatus recited in claim 1, wherein said plurality of secondary air nozzles comprise guide vanes attached to a portion of said outlet pipe which is disposed within said chamber, said guide vanes forming nozzles between said inlet pipe and the wall of said cylindrical chamber, and wherein said inlet pipe and guide vanes are axially movable with respect to said chamber.

4. The separator recited in claim 1, wherein said means for forming an annular gap comprises a symmetrical, streamlined body, axially disposed in said inlet pipe, and having a cross-sectional area which is at least one half of the cross-sectional area of said inlet pipe, for forming an annular gap about said body within said inlet pipe.

5. The separator recited in claim 4 wherein said inlet pipe is closed at its lower end with the lower end of said streamlined body resting thereon and wherein gas containing the particles to be separated is fed into the gap between said inlet pipe and said streamlined body through at least one tangential feed line which comprises said means for rotating.

6. The separator recited in claim 5, wherein said streamlined body is mounted within said inlet pipe so as to be interchangeable.

7. The separator recited in claim 6, wherein said streamlined body is interchangeable with another streamlined body having a different diameter.

8. The separator recited in claim 1, in which said means for rotating comprises a plurality of guide vanes disposed in said annular gap.

9. The separator recited in claim 1, wherein said inlet pipe is axially adjustable.

10. The separator recited in claim 1, wherein said plurality of secondary air nozzles comprises a plurality of guide vanes attached to a portion of the outlet pipe which is within the cylindrical chamber to form nozzles between said inlet pipe and the wall of said cylindrical chamber and wherein said inlet pipe and attached guide vanes are axially movable with respect to said chamber.

11. The separator recited in claim 1, wherein a plurality of said separators are connected in series to provide a plurality of stages with an increasing distance between the particle inlet and secondary nozzle ring from stage to stage.

12. A rotary flow particle separation apparatus, comprising:

a cylindrical centrifugal chamber;

a coaxial inlet pipe disposed at one end of said chamber;

a coaxial outlet pipe disposed at the other end of said chamber;

a plurality of secondary air nozzles disposed in a single annular arrangement for directing a flow of air tangentially. with respect to the inner surface of said chamber and at an angle towards said inlet pipe;

a particle outlet disposed concentrically about said inlet pipe; and

means for forming an annular gap at the outlet of said inlet pipe and including means for rotating particle laden gas introduced therethrough,

a plurality of said separators being coupled in series so as to provide a plurality of stages in which the distance between said particle inlet and secondary nozzles increases from stage to stage. 

1. A ROTARY FLOW PARTICLE SEPARATOR, COMPRISING: A CYLINDRICAL CENTRIFUGAL CHAMBER, A COAXIAL INLET PIPE DISPOSED AT ONE END OF SAID CHAMBER, ACOAXIAL OUTLET PIPE DISPOSED AT THE OTHER END OF SAID CHAMBER, A PLURALITY OF SECONDARY AIR NOZZLES DISPOSED IN A SINGLE RING ARRANGEMENT FOR DIRECTING A FLOW OF AIR TANGENTIALLY WITH RESPECT TO THE INNER SURFACE OF SAID CHAMBER AND AT AN ANGLE TOWARDS SAID INLET PIPE, THE DISTANCE BETWEEN SAID INLET PIPE AND SAID SECONDARY NOZZLES BEING ADJUSTABLE, A PARTICLE OUTLET DISPOSED CONCANTRICALLY ABOUT SAID INLET PIPE AND INCLUDING MEANS FOR ROTATING PARTICLE LADEN GAS INTRODUCED THERETHROUGH, AND MEANS FOR FORMING AN ANNULAR GAP AT THE OUTLET OF SAID INLET PIPE.
 2. The apparatus recited in claim 1, wherein said inlet pipe is axially adjustable.
 3. The apparatus recited in claim 1, wherein said plurality of secondary air nozzles comprise guide vanes attached to a portion of said outlet pipe which is disposed within said chamber, said guide vanes forming nozzles between said inlet pipe and the wall of said cylindrical chamber, and wherein said inlet pipe and guide vanes are axially movable with respect to said chamber.
 4. The separator recited in claim 1, wherein said means for forming an annular gap comprises a symmetrical, streamlined body, axially disposed in said inlet pipe, and having a cross-sectional area which is at least one half of the cross-sectional area of said inlet pipe, for forming an annular gap about said body within said inlet pipe.
 5. The separator recited in claim 4 wherein said inlet pipe is closed at its lower end with the lower end of said streamlined body resting thereon and wherein gas containing the particles to be separated is fed into the gap between said inlet pipe and said streamlined body through at least one tangential feed line which comprises said means for rotating.
 6. The separator recited in claim 5, wherein said streamlined body is mounted within said inlet pipe so as to be interchangeable.
 7. The separator recited in claim 6, wherein said streamlined body is interchangeable with another streamlined body having a different diameter.
 8. The separator recited in claim 1, in which said means for rotating comprises a plurality of guide vanes disposed in said annular gap.
 9. The separator recited in claim 1, wherein said inlet pipe is axially adjustable.
 10. The separator recited in claim 1, wherein said plurality of secondary air nozzles comprises a plurality of guide vanes attached to a portion of the outlet pipe which is within the cylindrical chamber to form nozzles between said inlet pipe and the wall of said cylindrical chamber and wherein said inlet pipe and attached guide vanEs are axially movable with respect to said chamber.
 11. The separator recited in claim 1, wherein a plurality of said separators are connected in series to provide a plurality of stages with an increasing distance between the particle inlet and secondary nozzle ring from stage to stage.
 12. A rotary flow particle separation apparatus, comprising: a cylindrical centrifugal chamber; a coaxial inlet pipe disposed at one end of said chamber; a coaxial outlet pipe disposed at the other end of said chamber; a plurality of secondary air nozzles disposed in a single annular arrangement for directing a flow of air tangentially with respect to the inner surface of said chamber and at an angle towards said inlet pipe; a particle outlet disposed concentrically about said inlet pipe; and means for forming an annular gap at the outlet of said inlet pipe and including means for rotating particle laden gas introduced therethrough, a plurality of said separators being coupled in series so as to provide a plurality of stages in which the distance between said particle inlet and secondary nozzles increases from stage to stage. 